Communication system



April 17, 1945- R. s. PlTKlN, JR

COMMUNICATION SYSTEM Filed Jan. 2, 1943 Patented Apr. 17, 1945 ooMMoioAnonsYsTnM. v nb'yfs Pitkin, Jr., Rubhe'steerfinn; Appiication January 2, 194e-, 'seialfNa mitos-4f eciaims. (ciirz'sflfi' g My? present-inventinf relates to improvements iii-intra-communicationf systems: of an amplified type, f andi it Ahaslbeen1especiallyfdesigned:for mili.

taryfus'e an'd`sim'lar`purposes.. `It'is'an'aixnv of my invention to" simplifyj the construction: of apparatiis l ofi'. th'e character' icontem'plated1 herein, and to imprdvetheloperation ot said apparatus;

Il-l'ave4 found that in'lmilit'ary tanks,` .half tanks, armored trliicks', planes, boats f andir like vehicle's, extrane'oiisl nois'esareI developedf` Within" the vehicle due to? motors',v vibrations and" analogous n'oise producing." equipment, sucht asl exploding guns, and such extranos'rioi-se'saretsogreat tli'at fco'rnmlinic'ationbetweenloccupants fo'fthe fveiri'mind, Ihavefprovidedanintraommunication e system' Whiclifrnakesitpossible forv` occupants of a'v vehicle4 which?- i'sl' subjecti to? such'lextraneous noises; i-,o` conver'selbetween-'themselves without effort. I have also providedl ai communicationsystemY whereinsu'ch# extraneous noisesi are? substantially inaudible to? ther" ea'r'slof the occupants, -Wiiile theivccal sounds' ar'elreadilyaudiblef thel` individual-` members thereof; ariy .typef lofrr headpl'ione"'lfiecomesI extremely hot and' itlisf'uneonifortablatowear due to the 'presi sure7 which it;A eiier-tsf against the 'delicate` cartilagesvofithe :human earl so'lthattheyy may beworn For: in@purpose'-V ofl disclo'sin'gfinns. invention-, 11

lia'v shown myJneW-and' improved communica;- tin" system installed inla 'military tank, .butit is not my intention to limit this invention tcuseinl militaryl tanks-as it'willlreadily 'befapiarent from the hereindeseribedapparatusthatfthis-invention mayL readii'y'ber adapted to be incorporated: into other vehicleswhere the'- extraneous "njoise's 'are-so When installed inE a niilitar'yy combatftank for Warfare' vand other uses, my neW-andimprovedap'- paratus isl adapted t'c provide idenite andv con'- tinuo'us communicatin at all'v tim'es hetwee'nfa central station and afpluralityfo'ff'substations;j 'the commander of the-tank occupyingl` a' position Which Will'eilablef 'hlm to talnsmit'and' receve'signals and'l nies'sage's fromf'the centr'al' station, f and the several membersof'hisicrew'- occupying p'o's'iitions iii pioXIityf the respective SilbStatO/DS, and'v'ice Versa', asialloffthe'cir'cits are constantly open; With" the exception o'fi the headphones which are'iuse'd b'yth'e commander-g" the emply`- m'en'tl' by` th'e crewv of these instrumentalities' Iand their" accessories such`IJ a's the lead cords"` and vthe like; is :entirely eliminated in' my intraconimu'nication system's'o that thereis no danger of'such accessories lo'e'eon'fiingfgl tangled* n or broken' by' the members "of" th'e'crew' Whjo are constantlyshifting positionsormovingaround at' their statinsn tneiponstrioted'- vc ompanini'enr within' janei ta'nj'k b'dy, Irl.` lieu.y Of'th'e' p'ilafble" Hdpl'sl'ai Also", 'theffideli-tyfo' these' instruir-lents fis unsatisj'- 'factoryT and'lips';v of'v relatively low orderi due' to?` the fact' that they;y laclvdamping? means" toIl` eliminate thefextraneoiisi noisessuch 'asf the roar-of' the'op: eratingzvehicle and the sounds fofthe 'explosions o'f-Ycannonfandvrother Weaponsiloothfinside'andout; si'de thef''ta'iilr"-soiv that the: vocalv sounds' fromfth'e commanders? microphone becc'mef mixedV with these` extraneou'srnoisesito such'aniectent that connnandersvocalf orders are indistinct and 'frequentlyi arefnot"dis'cernedby crewmembers. In the structure disclosed' I havefovercdme the 7afmiie'; mentioned disadvantagesiand o'lojecti'enable'V fea: ture-Whichlare' now 'p'resent'iin the'fa'pproved'y army equipment; j

With-in@ afi `certai type l off military! tank,l the commander." and# 3'T gunner and loaden occp'y a? chile-*turret and' thevother crewV mem;- bers'fincldirigthefdriver'andthe 75fn1m. gunner arfdlioaaer; .inside'ftnetank ccmpa'rtmenti must 'au useftneirhands, arms andfeet'inithe performance o'f their? respective du'tie's' andf when' eri'-,gf"aged in for' theint'nfianuall'y gra'sn afniicrophoneftwconversefWith-thefcoinmander It`l therefore will be se'enfthatf ther-present use'go'fy portable-micro'- `heard by the commander.

come deafened and cannot hear the orders given by the commander. When my improved intracommunicaticn system is used, the individual crew members may plug their ears to reduce the overall sound level and by increasing the volume of loud speakers at the crew stations, a greater ratio of voice to extraneous sounds will result so that the voice of the commander will becomemore intelligible to his crew.

In connection with structure contemplated herein I have devised a microphone structure which is of much smaller dimensions than those which have heretofore been employed in intracommunication systems of this character. The microphone is of the dynamic type and the diaphragm is exposed upon both sides to the extraneous sounds incident to the tank operation. This causes the extraneous sound waves to simultaneously strike upon both the front and rear sides of the diaphragm which will neutralize or balance the effect upon the diaphragm resulting in a cancelling or damping and non-vibration thereof. The diaphragm is suitably shielded so that the vocal sound waves of a crew member speaking into the microphone reach only one face of the diaphragmv which will cause the latter. to respond thereto and his voice From the foregoing it will be seen that, due to the shortcomings of the intra-communication system in vogue in themilitary tanks, the said system is ineiiicient and is incapable of satisfactory operation when the crew and tank is engaged in combat which is the time when the apparatus is most needed. In the novel and improved system which I have invented, the members of the crew do not wear headphones nor do they require portable microphones. The hands of the men are free at all times for'the performance of their various duties and carrying out the commanders orders, and conversation between the commander and his crew is possible at any time since all that a member need do is merely speak into the microphone installed at his station and the voice is heard by the commander through his earphones which have been designed for comfort as well as to block out or damp the roar of the tank and its equipment. The commanders microphone is supported adjacent his mouth upon a short flexible holder that is attached to one or both of his headphones which permits him to speak to the crew at all times without changing his position and without physical eiort. The volume of the loud speakers at the several crew stations is proporpermit the extraneous sound waves tosimultaneously strike the front and the rear faces of the microphones. This has a cancelling effect so tions have disclosed the extraneous noises which are so harsh and violent that a person within the tank cannot hear his own voice when shouting at a high pitch, yet the microphone will pick up that persons voice waves when they are spoke from a distance of several inches from the microphone and Will be distinctly heard through the commanders headphones to which these vocal sound waves are carried through an amplifier channel. The intra-communication system which I have invented is assembled as a unit so that it may be inserted into the standard Army approved shock-proof base where the usual radio that the diaphragms are practically inert in relation to the roar of the tank and the gun-rire,

but since the diaphragm is especially designed to pick up thevocal sound waves upon only one of its sides, these vocal waves will cause a vibration of the diaphragm so that the voices are audible. Actual tests with my intra-communication system installed in tanks and under combatA condireceiver and transmitter are also installed in the body of the tank and it is adapted tobe operated over the wires,` which are already installed for theV equipment now being used.

Other advantages and aims of my present improvements will be apparent to persons skilled in the art after the construction and operation of my dual channel amplified intra-communication is understood from the within description. Among these additional aims or objects may be mentioned that my invention aims to provide an apparatus that possesses a high degree of novelty; which is efdcient in the performance of itsvfunctions; which is madev of sturdy and dependable parts so as to render it capable of withstanding severe usage; which is comparatively economical to manufacture; and which may be installed in military tanksnow in use without altering the standard built-in structures and equipment. i

I prefer to accomplish the above-mentioned and other objects and aims, and to practice my invention in substantially the manner hereinafter described and as particularly pointed out in the appended claims. lReference is now made to the accompanying drawing which forms a part of this specification.

The drawing shows in diagrammatic form, of a more or less schematic character, a typical or preferred embodiment of my improved duel channel amplified intra-communication system, the various parts of the structure being illus- `trated rby means of mechanical and electrical phones structure, and it has relatively7 small dimensions as compared with the more or less standard types of devices being slightly over an inch in diameter and one-half inch in thickness. Said microphone is designed so that it may be disposed close to the commanders mouth teattain the best results from it, and its structure is ,such that it excludes extraneous sounds and 0perates at closerange or Valmost touching Vthe lips of the speaker. The microphone Il is adapted to respond to frequenciesof about 250 to 4000 cycles. As the range of hearing is approximately 40 to 18,000 cyclesjitwill ybe seen that the undesired sound waves outside the vocal range, those below 250 cycles and" those between 4000 and 18,000 cycles, will be eliminated and the sound waves picked up will be only the predominant waves of .250 -to 4000 cycles within the vocal range..- The conductors l2 and. I3 from microphone H -are .provided with -an insulating shield-,I4 and they lead ,to respective, terminalslwhich. bear thesym- 2;I. therein.4 ConductorsI I2a. and .I 3a. from. theinputf. device I5z-I6. in the microphone circuit, which'. are Iprovided with an insulating shieldI4a within the` box I1, pass .Out offthe latterand lead toz.dual channel amplifierv devices vwhichxare cons tructed tozadapt it-` to. be removably installed asl a unit inA a:- convenient.vv location `within thev com-A partment of l. the tank. The construction land ,di-- mansions `of this-.amplifier device-are such that, the., unit` will.; lit the army standard receptaclev Within fthe; tank without alteration .and .may be readilyfremoved whenever desired:

. In the diagram, the:` amplifier circuitsg for the commander and the crew have a-commonpower supply, schematically identiedas 2 2. The elements in the amplifier circuit -related'to the commanders microphone II comprise the microphone input transformer 23, the input tubef24,

andthe output transformer 25,;.and the latter transformer is electrically connected by-conductorz 26 with the terminal.l ofthe receptacle 2.1 which coacts with corresponding prong l of the multiple prong plug 28. A volume controldevice2|f is inserted in the conductorv 26. From. the prong 1v a conductorV 26a leads to one or more dynamic speakers 29, one ofwhich is shown,

whichare `placed at strategic locations or substations .convenient to the different crew members,.preferably at their respective stations. The

input device 30 for the microphone I I is contheexclusion ofi extraneousor. other Vsoundwaves outside the;vocalz'range.` Thezvocalsounds de'- livered by: the speakers .21S-lare extremely loudl in order"v to*v be heard: above-.the noisesofzrthe tankf and thegunre: 1.l The: microphone hasf no :resonant-'pouch or cavity.' and therefore emitsa' flat response; Theiamplier is also flat andztheloudv speakers reproduce a flat response.

The vocal; sounds leaving theloud speakersat- 0 the severalsubstationscare-quite;loud and of-.con-

sid'erafblel volumeto thechuman ear rdrums ofthe crew.. Theinears' are plugged. by mutingl plugs 5.05 to: reduce: the,-sound1vibration, upon .the ear diaphragm and avoid injury thereto; The human ear Vwillrreceive=sounds as they become progres-y sively -louder'f upzjto f a certain degree `and thereafter.: the ear; `will be.- unableto -translatefthe, sound fdue.V to the' natural 'structure .ofthe earL to` protect thenervoussystemto protectzthe person from intense head pains. The highest degree-of. soundwhich lthe average person can experience without pain is ratedat about 125 db.` (decibels) of'sound, as ycompared with 109-113 db. ofsound which I have ascertained is the normal degree of sound within the tank. I therefore increase the volume of sound issuing from the loudspeaker to. about 118 db.I which is a degree where the oral sounds are so loud that they are well above the extraneous noisesvinthe tankso as to bev intelligible to the crew members, but since these vocal sounds are so extremely intense they must amplifier circuit, although having Vmuch less power outputy and consists of microphone input transformer 4 I, the input tube 42`and the output transformer-43; Shielded conductors 44, 45 c on'-V nectthe terminals 2. and 3 ofthe input device 39"with the input'transformer 4I. `A conductor 46 .leads from Outputtransformer 43 'to a. jack 41 and a branch conductor 40a` leads toa terminal 5 ofthe receptacle 21 which coacts with corresponding prong "5 of the multiple prongV plug 28 from which prong'f5 a non-shielded conductor. 48 leads into the control boxi I1`and thence by conductor 48a to the volume control device 2|. A volume control device 2|" is-inserted inthe conductor 46. y

The-f commanderrspeaks into his central station microphone I I and the sound waves are fed into the channel of the amplifier circuit, the upper circuit inthe diagram, of the dual channel amplifier devices. The output of this amplifier circuit is then fed into the loud speakers at the ,crew stations or substations within the tank.

up sound waves which are predominately vocal to be muted byv deafeningthe crew bymeans. of

plugs 50 inserted intotheir ears. This mayfcause. y

a drop in .sound volume reaching the ears to db.A (the tank noise) and the 118. db. Voice to 95 db. Intelligibility at this Vdegree may be found to be lcw'but this is .readilyovercome byfurther increasingfthe volume of. the loudspeakr untill the degree of. sound reaching the ear drumsis back to 118 db. Obviously this results in a high". ly favorable voice to noise ratio and results in a high )degree of intelligibility They crew may converse with the commander by means of' their dynamic microphones units 36a, 36h, etc., from whence the vocalwaves are fedinto'the second channel of the amplier and then tothe commanders headphones I0. Each unit 36d is provided with a Ipaper diaphragm and a.v moving voice coil andthe'diaphragm is exposed onboth sides'v to allow the tank noises and gun re sound energy to hit the front and back' facesfand cancel out the extraneous noises. becausethese .is no .apparentmotion in the voice coil..A The Voice of acrewmember will hit 'the frontof .this diaphrgm and thus a very favorable ratiov of vocal sound waves to extraneous sound waves isattained.v

4Although but one specific embodimentof this inventionis herein described, it is to be understoodl that some ofthe vdetails setiforth may be altered or omittedwithout departing from the spirit of'theinvention as den'ed'by the following claims.

1. An intra-communication system for vehicles of the enclosed type wherein noises from eXtraneous sources are inherent embodying a central station microphone; a substation microphone: dual channel amplifier circuits for said microphones; a common power supply for said amplier circuits; each said circuit consisting of an in-put transformer, an in-put tube, and an output transformer; a loud-speaker in one of said amplier circuits; headphones in the other of said amplifier circuits; one of said microphones being in circuit relation with said loud-speaker and the other of said microphones being in circuit relation with said headphones, control means in said loud-speaker amplifier circuit effective to raise the volume of sound delivered by said loudspeaker to a level above that of the extraneous noises vand above the level of sound volume that the human ear can safely receive, and sound modifying means interposed between the loudspeaker and the car of the operator in proximity thereto and positioned to betraversed by sound waves from said loud-speaker and from said extraneous sources to simultaneously reduce the volume of sounds delivered to the ear of said operator to a level within the range of sound volurne that can be safely received by the human ear, to thereby increase the differential of sound volume between the noises from said extraneous sources and the signal sounds as received by said operator.

2. In an yintra-communication telephone system including a central station and a substation, each comprising a microphone and a receiver, and both stations being positioned in an environment characterized by the presence of high decibel noises from extraneous sources, means to increase the volume of signal sound from the receivers to a decibel level above that of the noises from said extraneous sources and above that which the human ear can safely receive, and

muting means interposed between the said receivers and the ears of operators effective to reduce simultaneously and in corresponding amount the decibel level of both the extraneous sounds and signal sounds to within a decibel range which the human ear may safely receive to thereby increase the differential between the decibel level of the signals and of the sound from said extraneous sources as received by the operator.

3. In an intra-communication tele-phone system including a central station and a substation, each comprising a microphone and a receiver, and both stations being positioned in an environment characterized by the presence of high decibel noises from extraneous sources, means for neutralizing the effect of sound from said extraneous sources upon said microphones, means to increase the volume of signal sound from the receivers to a decibel level above that of the noises from said extraneous sources and above that which the human ear can safely receive, and muting means interposed between the said re- 'ceivers and the ears of operators effective to reboth stations being positioned in an environment' characterized by the presence of noises from extraneous sources of a volume close to but less than the upper decibel level which the human ear may safely receive, means to neutralize the effect of the sound waves from said extraneous sources upon said microphones, means to increase the volume of signal sound from said receivers to a decibel level above that of the extraneous noises and above that which the human ear can safely receive, and muting means interposed between the said receivers and the ears of the operators effective to reduce simultaneously and in corresponding amount the decibel level of both the extraneous sounds and signal sounds to within a decibel range which the human ear may safely receive to thereby increase the diierential between the decibel level of the signals and the sounds from said extraneous sources as received by the operators.

5. In an intra-communication telephone system including a central station and a substation each comprising a microphone, the substation including a loud-speaker receiver, and both stations being positioned in an environment characterized by the presence of high decibel noises from extraneous sources, means to neutralize the eiect of the sound waves from said extraneous sources upon said microphones, means to increase the volume of signal sound from said loudspeaker to a decibel level above that of the extraneous noises and above that which the human ear'can safely receive, and muting means adapted to be disposed in the ears of operators at said substation and effective to reduce simultaneously and in corresponding amount the decibel level of both the extraneous sounds and the signal sounds from the loud-speaker to within a decibel range which the human ear may safely receive to thereby increase the differential between the decibel level lof the signals and of the sounds from said extraneous sources as received by the operators.

6. In an intra-communication telephone system including a central station and a substation g each comprising a microphone and a receiver, the

receiver of the substation being in the form of a loud-speaker, and both stations being positioned in an environment characterized by the .presence of high decibel noises from extraneous sources, means for neutralizing the effect of sound from said extraneous sources on said microphones, means to increase the volume of signal sound from the loud-speaker to a decibel level appreciably above that of the noises from said extraneous sources, and muting means adapted to be disposed in the ears of an operator at the substation and eiective to simultaneously reduce and in corresponding amount the dicbel level of both the extraneous sounds and signal sounds to thereby increase the differential between the decibel level of the signals and of the sounds from said extraneous sources as delivered to said operator.

ROY S. PITKIN, Ja. 

